Luminescent display with a memory and a heat-quenching element



Sept. 15, 1970 R, HANSEN 3,529,155

LUMINESCENT DISPLAY WITH A MEMORY AND A HEAT-QUENCHING ELEMENT FiledMarch 15, 1967 SOURCE OF ULTRA-VIOLET LIGHT I2 --34 PULSE GENERATOR l4mx 1/ HEAT-GENERATOR LUMINES T 3 ELEMENT SURFAC '1 HEAT- QUENCHABLEINVENTOR RAYMOND J. HANSEN BY fiX HIS ATTORNEYS United States PatentU.S. Cl. 250-71 4 Claims ABSTRACT OF THE DISCLOSURE A heat-quenchablelayer, such as zinc-cadmium-sulfide, that is activated by nickel, isbathed in ultra-violet light to produce a fluorescent display surface.This display surface is placed adjacent to a heat-generating element.The heat-generating element is in heat-conducting relationship with thefluorescent display surface and is associated with a ferrite memory corewhich operates in a partial switching mode. A high-frequency A.C. signalapplied to the 'ferrite memory core is coupled through the memory coreto the heat-generating element with a large amplitude when the memorycore is in one memory state and with a small amplitude when the memorycore is in the other memory state. The state of the memory core isdetermined by a pulse-switching means which causes partial switching ofthe ferrite memory core. Therefore, when the memory core is in onememory state, the heat-generating element receives a large amount ofenergy, which is converted into heat that quenches the fluorescing stateof the memory device in the vicinity of the heat-generating element.When the memory core is in the other memory state, however, the amountof energy received from the A.C. signal source is not sufiicient toexceed the heat-quenching threshold of the fluorescent display surface.

CROSS-REFERENCES TO RELATED APPLICATIONS (l) Luminescent Display System,by George T. Brown, Jr., U.S. patent application Ser. No. 503,989, filedOct. 23, 1965.

(2) Luminescent Display with a Memory, by Raymond J. Hansen, U.S. patentapplication Ser. No. 598,038, filed Nov. 30, 1966.

BACKGROUND OF THE INVENTION U.S. patent application Ser. No. 503,989,entitled Luminescent Display System and filed Oct. 23, 1965, in the nameof George T. Brown, In, discloses a visual display which employs adisplay panel which in the presence of ultra-violet light becomes alight source, emitting a color characteristic of the fluorescentmaterial that is coated on the surface of the display panel. When aselected heat pattern is placed adjacent to the display panel, thefluorescent material in the vicinity of the heat pattern is quenchedfrom its characteristic light-emitting state, and a data pattern isdisplayed when the display panel is exposed to ultra-violet light. Thedisplay panel disclosed in the above-cited Brown U.S. patentapplication, Ser. No. 503,989, can be selectively employed in a numberof different display systems. However, this display panel does not havean inherent memory directly associated with it. Therefore, when adecoding matrix "ice is employed to select the desired heat pattern, itis necessary to insure that the elements in the decoding matrix arecontinually held at some fixed level during display of the desiredpattern. The present invention provides a display panel which has itsown memory; therefore, once a display pattern is conveyed to the displaypanel of the present invention, the display panel remembers the pat--tern until a new pattern is to be displayed.

U.S. patent application Ser. No. 598,038, filed Nov. 30, 1966, in thename of Raymond J. Hansen, discloses a heatquenchable luminescentdisplay system that operates in combination with a magnetic memoryselection network. In this application, it is the hysteresis energy lossof a magnetic memory core which quenches the fluorescing state of theluminescent display panel. Therefore, it is essential in thisapplication that the magnetic memory element be positioned in closeproximity to the luminescent display panel. The present invention,however, provides a magnetic memory core which utilizes a heatingelement that may be located at a position which is remote from themagnetic memory core, thereby greatly simplifying construction of aluminescent display panel with a memory.

SUMMARY OF THE INVENTION A readout surface of fluorescent material in aheatquenchable fluorescing state is placed in proximity to aheat-generating element. The heat-generating element is associated witha magnetic memory core which operates in a partial switching mode. Ahigh-frequency A.C. generator is coupled to the magnetic memory core,whereby, when the magnetic memory core is in one memory state, a largeA.C. signal is coupled through the memory core to the heat-generatingelement, thereby creating a large amount of heat, which quenches thefluorescent state of the fluorescent material in the vicinity of theheat-generating element. When the magnetic memory core is in the otherstate, however, only a very small amount of A.C. signal is coupledthrough the memory core to the heat-generating element, and, as aresult, the heat generated in the heat-generating element is notsuificient to quench the fluorescing state of the adjacent fluorescentmaterial.

BRIEF DESCRIPTION OF THE DRAWING The figure shows the luminescentdisplay and memory system of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The figure represents an elementof a display employing the present invention, which utilizes theheat-generating element 10, which is placed adjacent to a surface 18,which is coated with a suitable fluorescent material. For example, atroom temperature, a superior material of fluorescent properties for usein practicing the present invention is zinc-cadmium-snlfide, which isactuated by silver and poisoned by nickel, as set forth in the publishedarticle Fluorescent Thermograph, by W. H. Byler and F. P. Hays,appearing in the May-June 1961 issue of Non- Destructive Testing; and inU.S. Pats. Nos. 2,551,650, and 2,642,538, issued May 8, 1951, and June16, 1953, respectively, on applications of Franz Urbach.

A magnetic memory core, such as the core 12 of the figure, whichoperates in a mode of operation similar to the mode of operation of thememory core in the present invention, is disclosed in US. Pat. No.3,281,802, issued Oct. 25, 1966, on the application of Robert E.McMahon. However, the McMahon magnetic memory core was employed in anentirely dilterent environment, in that it was employed to generate aconventional memory output signal and not to generate heat for locallyheat-quenching a luminescent display panel, to form a visual displaypattern.

If the magnetic core 12 has an original flux state, as shown by thearrow 20, then a pulse of current through the winding 24, produced bythe pulse generator 14 in the direction indicated by the arrow on thewinding 24, will tend to reverse the magnetic flux state of the magneticcore 12. This reversal of magnetic flux state begins at the innersurface 26 of the magnetic core 12 and progresses to the outer surface23. Therefore, termination of the current pulse in the winding 24 beforethe flux state has reached the outer surface 28 will result in areversal of magnetic state only in the area 30.

The described partial switching phenomenon makes it possible toconstruct a sine wave non-destructive magnetic circuit. The AC. sinewave current generator 32, which is coupled to the magnetic core 12 bythe winding 36, will produce a large A.C. signal on the winding 38whenever the areas 30 and 40 are in the opposite flux states, asindicated in the figure by the arrows 20 and 22. If, however, the areas30 and 40 are in the same flux statesthat is, if the arrows 20 and 22are in the same directiononly a small A.C. signal will appear on thewinding 38. Thus, when the core 12 has been switched to a partiallyreversed magnetic state, the heat-generating element 10, which may beany resistive heat-conducting element (for example, a Nichrome or atantalum film or wire may be used), will produce sufl'icient heat toquench the luminescent surface 18, which is bathed in ultra-violet lightemitted by a source of ultra-violet light 34 to achieve a characteristicluminosity, in the vicinity of the heatgenerating element 10. When themagnetic memory core 12 is in the other memory state, theheat-generating element does not receive sufficient energy from thewinding 38 to exceed the heat-quenching threshold of the luminescentsurface 18. The magnetic memory core 12 may be reset into the statewhere the areas 30 and 40 have the same magnetic flux direction simplyby supplying a reset current to the winding 24, in the directionopposite to the arrow on the winding 24, from the pulse generator 14. Itis not necessary to apply a continuous sine wave signal to the memorycore to maintain the magnetic state of the memory core. Magnetic memorydevices of this type may expect a zero to one output signal ratio ofgreater than twenty to one.

Although a particular configuration for obtaining a display isdisclosed, it is apparent that the present invention may also bepracticed by a number of methods that are apparent to those skilled inthe art. In particular, it is apparent that a display pattern on thefluorescent surface of the present invention may be formed ofrectangular areas which correspond in area to the area of a rectangularheat-generating element, or, alternately, they may be formed by placingheat-conducting surfaces which are formed into character shapes close tothe heat-generating elements of the present invention, between theheat-generating elements and the fluorescent surface. Therefore,limitation of the invention in this respect to the described embodimentis not intended.

The present invention may be used to produce a luminous display againsta dark background, and a number of other prior-art schemes may also beemployed to achieve variations of the present invention which areobvious to those skilled in the art and are intended, therefore, to beincluded within the scope of this invention. In particular, theprinciples of this display are not limited to the display of numerals,and modifications of this display include other symbols and patternsthat will be obvious to those skilled in the art. Furthermore, a numberof fluorescent materials are known which produce dilferentcharacteristic colors, and those skilled in the art may therefore employthe teachings of this invention in display systems which employmulti-color luminosity.

Typical values for the present circuit may be a ferrite core of from50-rnil inside diameter to -mil outside diameter, an alternating currentampere-turns value of 700, an output winding of 15 turns, a set currentof 1 ampere-turn with a 1.0-microsecond width, and a reset current of 1ampere-turn at 0.2-microsecond width and an A.C. sine wave currentsource with a frequency of 10 m'egacycles.

What is claimed is:

1. A display system comprising:

(A) A readout area of thermally sensitive material which inhibits anoptically detectable heat-produced change of state when sutficient heatis supplied to the readout area, and

(B) An electrically resistive heat-generating element positionedadjacent to the readout surface, and

(C) A magnetic memory core, and

(D) An alternating current source coupled to the magnetic memory core,and

(E) An output winding coupled to the magnetic memory core and to theelectrically resistive heat-generating element, and

(F) Means coupled to the core to magnetically switch a portion of thecore, a relatively large amount of energy being coupled from thealternating current source to the electrically resistive heat-generatingelement through the output winding whenever the portion of the core isswitched, thereby supplying heat to the readout area, a relatively smallamount of energy being coupled from the alternating current source tothe electrically-resistive heat-generating element through the outputwinding whenever the portion of the magnetic memory core is notswitched, so that the thermally sensitive material is unheated in thiscondition.

2. A display system as in claim 1 wherein the electrically resistiveheat-generating element is shaped into a pattern to be displayed.

3. A display system as in claim 2 wherein the thermally sensitivematerial is a fluorescent material that is in a heat-quenchablefluorescing state when unheated and bathed in ultra-violet light.

4. A display system comprising:

(A) A readout area of fluorescent material which has a heat-quenchablefluorescent state when bathed in ultra-violet light, and

(B) A source of ultra-violet light located with respect to the readoutarea so that it is bathed in ultraviolet light, and

(C) An electrically resistive heat-generating element positionedadjacent to the readout area, and

(D) A magnetic memory core having a single aperture therein, and

(E) An alternating current source coupled to a first input winding onthe magnetic memory core, and

(F) An output winding on the magnetic memory core coupled to theelectrically resistive heat-generating element, and

(G) A pulse generator coupled to a second input winding on the magneticmemory core to magnetically switch a portion of the magnetic memorycore,

a relatively large amount of energy being coupled from the alternatingcurrent source to the electrically resistive heat-generating elementthrough the output winding whenever the portion of the magnetic memorycore is switched, thereby supplying heat to the readout area andheat-quenching the fluorescent state of the fluorescent material in thevicinity of the electrically resistive heat-generating element,

magnetic memory core is not switched, so that 5 the fluorescing state ofthe fluorescing material in the vicinity of the electrically resistiveheatgenerating element is not quenched in this condition.

6 References Cited UNITED STATES PATENTS 3,415,991 12/1968 Asars 250--833,452,199 6/ 1969 Stahlhut 2507 1 X ARCHIE R. BORCHELT, Primary ExaminerUS. Cl. X.R.

